This invention relates to a process for liquefying coal using electromagnetic wave energy defined as having wavelengths of from about 0.001 to about 100 A. Typical sources of such electromagnetic waves are the x-ray tube and .gamma. rays of radioactive substances. It particularly relates to a process for liquefying coal using a selective solvent and subjecting the solvent-coal mixture to x-ray energy or .gamma. rays.
It has long been known that hydrocarbon gases, liquids, pitch, and chemicals may be obtained in useful form from coal which is mined from the earth. Usually, the prior art has employed destructive distillation or other gasification processes for the conversion of coal into valuable liquid hydrocarbon products. Recently, the prior art has developed a high pressure hydrogenation of coal technique to effectuate such conversion. Still more recently, methods involving solvent extraction techniques have been developed for obtaining useful fuels and chemicals from coal whereby the coal is contacted with a selective solvent which acts as a hydrogen-donor for supplying sufficient hydrogen to the coal to aid in converting it into a liquid state.
Following the solvent extraction step, the prior art schemes have utilized various recovery procedures, such as hydrogenation of the liquid coal extract for increasing its value and utility together with retorting or coking of the residual materials obtained from the solvent extraction step to still further convert these coal derived products into more commercially valuable products.
However, the aforementioned prior art procedures have not been substantially commercially attractive or feasible to warrent widespread commercial exploitation of converting coal into valuable normally liquid products. Generally, the deficiencies in the prior art schemes have not only involved capital investment problems and disposal problems of the residue or waste frequently having high metals content, but have also involved liquid product quantity and quality problems which have yet to be solved in an economical and facile manner.
In U.S. Pat. No. 3,503,865, the prior art has taught the use of microwave energy in the conversion of coal into liquid hydrocarbon products.
We have discovered that electromagnetic waves having wavelengths of from about 0.001 to about 100 A, and in particular x-rays, are useful for the conversion of coal into valuable hydrocarbon products.
The radiation of Athabasca tar sands, aromatic hydrocarbons, waste water, petroleum oil, petroleum bitumen, kerosene and petrochemicals is known.
Since it is clear to those skilled in the art that the vast mineral resources of bituminous coal represent an extremely important supply of energy and an extremely important source of raw materials for valuable chemicals, it would be desirable to improve upon the prior art techniques, particularly the solvent extraction technique, in order to reduce the cost of obtaining high quality petroleum-type normally liquid products from coal.